Systemic lupus erythematosus (SLE) is associated with an increased risk of cardiovascular disease (CVD). Thromboprophylaxis with low-dose aspirin (ASA) and hydroxychloroquine (HCQ) seems promising in SLE. We investigated the effects of HCQ cumulative dosages (c-HCQ) and the possible synergistic efficacy of ASA and HCQ in preventing a first CV event (CVE) in patients with SLE.

Patients consecutively admitted to our center who, at admission, satisfied the 1997 American College of Rheumatology and/or 2012 Systemic Lupus Collaborating Clinics classification criteria for SLE, and had not experienced any CVE, were enrolled. The occurrence of a thrombotic event, use of ASA, and c-HCQ were recorded. Kaplan-Meier analysis was performed to determine the c-HCQ associated with a lower incidence of CVE. Cox regression analysis served to identify factors associated with a first CVE.

For the study, 189 patients with SLE were enrolled and monitored for 13 years (median). Ten CVE occurred during followup. At Kaplan-Meier analysis, the CVE-free rate was higher in ASA-treated patients administered a c-HCQ > 600 g (standard HCQ dose for at least 5 yrs) than in patients receiving ASA alone, or with a c-HCQ dose < 600 g (log-rank test chi-square = 4.01, p = 0.04). Multivariate analysis showed that antimalarials plus ASA protected against thrombosis (HR 0.041 and HR 0.047, respectively), while antiphospholipid antibodies (HR 17.965) and hypertension (HR 18.054) increased the risk of a first CVE.

Our results suggest that prolonged use of HCQ plus ASA is thromboprotective in SLE and provides additional evidence for its continued use in patients with SLE.